Probing $Z$-$Z'$ mixing with ATLAS and CMS resonant diboson production data at the LHC at $\sqrt{s}=13$ TeV

TL;DR

This paper uses ATLAS and CMS LHC data at 13 TeV to set new limits on the properties of hypothetical $Z'$ bosons, significantly improving previous constraints and testing extensions of the Standard Model.

Contribution

First to present $Z'$ exclusion regions in the $\xi-M_{Z'}$ plane using 13 TeV LHC data, surpassing previous bounds from Tevatron and earlier LHC runs.

Findings

Extended the $Z'$ exclusion region in the $\xi-M_{Z'}$ plane.

Constraints on $Z$-$Z'$ mixing are more stringent than electroweak data analysis.

Potential for further improvements with higher luminosity data.

Abstract

The study of electroweak boson pair production provides a powerful test of the spontaneously broken gauge symmetry of the Standard Model (SM) and can be used to search for new phenomena beyond the SM. Extra neutral vector bosons $Z'$ decaying to charged gauge vector boson pairs $W^+W^-$ are predicted in many scenarios of new physics, including models with an extended gauge sector. The diboson production allows to place stringent constraints on the $Z$-$Z'$ mixing factor $\xi$ and $Z'$ mass, $M_{Z'}$. We present the $Z'$ exclusion region in the $\xi-M_{Z'}$ plane for the first time by using data comprised of $pp$ collisions at $\sqrt{s}=13$ TeV and recorded by the ATLAS and CMS detectors at the CERN LHC, with integrated luminosities of 13.2 and 35.9 fb$^{-1}$, respectively. The exclusion region has been significantly extended compared to that obtained from the previous analysis performed with Tevatron data as well as with LHC data collected at 7 and 8 TeV. Also, we found that these constraints on the $Z$-$Z'$ mixing factor are more severe than those derived from the global analysis of electroweak data. Further improvement on the constraining of this mixing can be achieved from the analysis of data to be collected at higher luminosity.